Emanuel, who just celebrated his first anniversary in office, had wanted to kickstart his mayoralty by showcasing the city to the world and his connections to power. Chicago is not only Barack Obama's hometown; Emanuel was his chief of staff. What better way to prove he had the president's ear than to announce that two of the biggest international political events were coming to town.

Unfortunately for Emanuel, if the summits were easier to get than the Olympics they were also easier to take away. In March, the White House abruptly announced that the G8 would be moved to Camp David, leaving Chicago with just Nato. Emanuel, who was given just an hour's notice of the change, was reported to be crestfallen and vexed.

The real reason for the decision is not known. Obama unconvincingly claimed Camp David would "provide a more intimate setting".

A more plausible explanation, even if it has been firmly denied, was a fear that Chicago would be turned into an unseemly battlefield between protesters and police, thereby making the president's hometown the focus of unflattering press coverage less than six months before the election.

"And if they don't listen … then with Gandhian ferocity, we'll flashmob the streets, shut down stock exchanges, campuses [and] corporate headquarters … we'll make the price of doing business as usual too much to bear."

At the Lockdown Bar and Grill on Western Avenue, you can order Anarchy on a plate, an Arson burger, and the Citizen's Arrest sandwich. There have already been eight arrests after a Catholic Workers group attempted to enter Obama's campaign headquarters on Monday. On Tuesday, about 100 protesters held a solidarity march against global police oppression in the city's mostly black South Side.

Th

Police and protesters clash in 1968. Photograph: AP
e last time protesters clashed with the authorities in Chicago while the world was watching was the 1968 Democratic convention. Back then,
a police riot exposed tensions within the Democratic party, and the city seared itself in the national memory after news anchor Dan Rather
was beaten to the floor by security guards.

Chicago has hosted many big events since then, including the Democratic convention in 1996 and Obama's victory speech in 2008. Police say they are no longer haunted by 1968, but fear a rerun of a more recent flashpoint.

"It's about Seattle," executive director of the Police Executive Research Forum, Chuck Wexler, told the Chicago Tribune. "That's the turning point." To that end, authorities have already flooded the Loop – the downtown area – with scores of police. Suitably enough, given that it's a Nato summit, Chicago is rapidly acquiring the sense of being under occupation.

This, says one of the protest organisers, Keeanga Yamahtta-Taylor, was the point. "The whole preparatory work has been to create a climate of intimidation," she says. "They want to project overwhelming force so that if you were thinking about maybe coming down and taking part, you'll think again." Just over half the city believed the protests would be peaceful.

It is revealing that Chicago was one of the few cities in the country not to have an Occupy encampment after attempts to set one up in Grant Park led to a slew of arrests.

Lawyers for the defendants argued that the aggressive policing served as a show of force that Chicago was a safe venue for the summits – and as a dry run.

Emanuel is a notoriously foul-mouthed centrist who once mailed a dead fish to a pollster who he accused of costing his candidate an election. When he was inaugurated, he said: "I am not a patient man. I will not be a patient mayor."

In preparation for the summit, he has tightened rules on demonstrations, raising fines for violators, and has demanded a $1m insurance policy for those seeking a permit.

Rahm Emanuel with Jennifer Hudson former boss Barack Obama at a Democratic event in 2011. Photograph: Jim Young/Reuters
l is motivated by a desire to reposition from the city from the capital of the midwest to a global player. "There's an ongoing debate here about Chicago's place on the world stage," explains Mick Dumke, an investigative reporter for the Chicago Reader. "We have a lot of international business here and one of the busiest airports in the world. But a lot of Chicagoans are sensitive to the accusation that it's too provincial. We're the third largest city in the country by size. But they fear we're a distant third in influence."

No cost-benefit analysis has been produced, or case made as to how the Nato summit would materially benefit a city that has been cutting services and raising taxes to meet balance its budget.

"This wasn't a city-wide decision," said Leslie Hairston, one of the few aldermen to vote against the mayor's summit ordinances. "Where is the economic boom going to be? These people are not going to be shopping at Garrett's Popcorn or going to the Museum of Science and Industry."

Over the past 40 years the most common reason for Chicago mayors to be voted out of office is their inability to effectively clear the snow. Emanuel has been lucky with a mild winter. This weekend he's hoping nobody rains on his parade.